The battery is the main source of power to the computer. Often times batteries will lose charge and need to be replaced. If the laptop won't turn on without the power cable, use this guide to replace the battery.
Using the JIS #0 Screwdriver, unscrew the ten 10 mm screws that hold the back casing in place.
Pry open the back casing using the opening tool along the side crevice.
Using the JIS #0 Screwdriver, remove the five 5.0 mm screws that hold down the battery.
Disconnect the cable connected to the motherboard.
To remove, lift the ends using the opening tool.